CANBERRA -- Acting Opposition Leader Tanya Plibersek has slammed the Turnbull Government's back down on proposed superannuation changes as an "incredible capitulation" to conservative Coalition backbenchers.

A day after securing Labor support for the passage of the $6.3 billion omnibus bill, the government has dumped a key but controversial budget measure, a lifetime cap of $500,000 on non-concessional super contributions.

The proposal of a lifetime cap was unpopular with the Coalition backbench including Queensland MP George Christensen who threatened to cross the floor.

The $500,000 lifetime non-concessional cap will be replaced by a new measure to reduce the existing annual non-concessional contributions cap from $180,000 per year to $100,000 per year;

Individuals aged under 65 will continue to be able to 'bring forward' three years' worth of non-concessional contributions in recognition of the fact that such contributions are often made in lump sums;

Individuals with a superannuation balance of more than $1.6 million will no longer be eligible to make non-concessional (after tax) contributions from 1 July 2017.

Mr Morrison described the changes as "fairer" and "more flexible" and said the government wants to help people achieve the "trifecta of Australian dreams" -- having children, owning your own home and saving for your retirement.